1. Field of the Invention
This invention relates to an electronic unit mounted to an engine. In particular, the invention relates to mounting an electronic unit to a gas turbine engine in such a way that that it forms part of the surface of the engine.
2. Description of the Related Art
A typical gas turbine engine may be provided with one or more electronic units, which may be referred to as electronic control units (ECUs), which may have the function of controlling and/or facilitating processes performed by the gas turbine engine and/or components of the gas turbine engine. Such ECUs may include one or more engine electronic controllers (EECs) and/or one or more engine health monitoring units (EMUs).
Typically, connecting an ECU to a gas turbine engine involves mechanically fixing the unit to the rest of the engine, and connecting a number of different electrical wires and/or harnesses in order to connect the ECU to one or more electrical systems of the engine. This is typically a time consuming and relatively complex process.
In other words, in a conventional arrangement, an ECU is electrically connected to wires in an electrical harness, which generally comprises multiple electrical wires and/or cables that may be generally flexible so as to be manipulated around the engine, and that may be surrounded by an insulating sleeve, which may be braided or have a braided cover.
Such an electrical harness is for transferring electrical power, and signals (which may be generated/received by an ECU) to and from electrical components/systems of the gas turbine engine. Such components/systems may serve, for example, to sense operating parameters of the engine and/or to control actuators which operate devices in the engine. Such devices may, for example, control fuel flow, variable vanes and air bleed valves. The actuators may themselves be electrically powered, although some may be pneumatically or hydraulically powered, but controlled by electrical signals. Thus, such conventional harnesses may be used to transmit signals, for example control signals, between the ECU(s) and the electrical components/systems of the gas turbine engine.
By way of example, FIG. 1 of the accompanying drawings shows a typical gas turbine engine including two conventional wiring harnesses 102, 104, each provided with a respective connector component 106, 108 for connection to circuitry, which may be for example accommodated within the airframe of an aircraft in which the engine is installed.
The harnesses 102, 104 are assembled from individual wires and cables which are held together over at least part of their lengths by suitable sleeving and/or braiding. Individual wires and cables, for example those indicated at 110, emerge from the sleeving or braiding to terminate at plug or socket connector components 112 for cooperation with complementary socket or plug connector components 114 on, or connected to, the respective electrical components. The FIG. 1 example has an ECU 120. The ECU 120 is connected to the harnesses 102, 104 using connectors 122, 124 respectively. The ECU 120 would typically also be connected to other wires/harnesses, which are not labelled in FIG. 1 to aid clarity.
Thus the conventional electrical harness 102, 104 has to be provided with plug or socket connector components 112, 122, 124 for connection to other electrical components, such as ECUs. These conventional plug or socket connector components add weight and complexity to the electrical harnesses. Furthermore, the conventional plug or socket connectors are exposed to the engine environment. Thus, the conventional plug or socket connectors may be exposed to, for example, high temperatures and/or vibrations. The exposed connectors therefore need to be particularly robust in order to survive this environment. This means that the conventional exposed connectors are bulky and heavy. Even such bulky and heavy connectors may still be susceptible to damage and/or becoming loose, for example due to engine vibration.
Each of the conventional harnesses 102, 104 comprises a multitude of insulated wires and cables. This makes the conventional harness 102, 104 itself bulky, heavy and difficult to manipulate. The conventional harnesses occupy significant space within a gas turbine engine (for example within the nacelle of a gas turbine engine), and thus may compromise the design of the aircraft, for example the size and/or weight and/or shape of the nacelle.
Conventional harnesses comprise a large number of components, including various individual wires and/or bundles of wires, supporting components (such as brackets or cables) and electrical and/or mechanical connectors. This can make the assembly process complicated (and thus susceptible to errors) and/or time consuming. Disassembly of the conventional harnesses (for example removal of the conventional harnesses from a gas turbine engine during maintenance and/or disconnection of the conventional harnesses from other components, such as the ECU) may also be complicated and/or time consuming. Thus, in many maintenance (or repair or overhaul) procedures on a gas turbine engine, removal and subsequent refitting of the conventional electrical harness and/or connected ECU(s) may account for a very significant proportion of the operation time and/or account for a significant proportion of the potential assembly errors.
The electrical conductors in the conventional harnesses may be susceptible to mechanical damage. For example, mechanical damage may occur during installation (for example through accidental piercing of the protective sleeves/braiding) and/or during service (for example due to vibration). In order to reduce the likelihood of damage to the conductors in a conventional harness, the protective sleeves/braiding may need to be further reinforced, adding still further weight and reducing the ease with which they can be manipulated. Similarly, the exposed electrical connectors used to connect one conductor to another conductor or conductors to electronic units, such as the ECUs, may be susceptible to damage and/or may add significant weight to the engine.
The wires and/or harnesses to which the ECUs are connected are usually enclosed within the engine, and thus once the ECU has been connected to the wires/harnesses, the ECU is usually covered by other components of the engine, and concealed by a gas-washed surface. Thus, once assembled, ECUs in a conventional arrangement are hidden and inaccessible from the outside of the assembled engine.
For example, an EEC of a conventional turbofan engine may be mounted on a fan case, for example using individual mounting brackets. Such an arrangement is shown in FIG. 2, in which an ECU 120 is mounted in a conventional way to a fan case 130 of a turbofan engine 100. The conventional complex arrangement of harnesses/cables is not shown in FIG. 2 to aid clarity. However, during assembly, the ECU 120 is manually connected to various flexible electrical wires and/or harnesses, and mechanically mounted to the fan case 130, in a time-consuming and relatively complex procedure. The electrical system, including the ECU and any wires/harnesses/connectors, must then covered by a gas-washed surface. In the case of an EEC (or other electronic unit) mounted on a fan case, such as that shown in FIG. 2, the enclosing gas-washed surface is commonly a nacelle (also not shown in FIG. 2 to aid clarity). Thus, in order to access the EEC, for example for maintenance/repair/replacement, the nacelle must be opened. Often, hinged panels, commonly referred to as fan cowl doors, are provided on the nacelle to allow access to the EEC. Opening the panels is a time consuming process, especially for larger engines in which a machine is required to lift and/or support the large, heavy panels. Furthermore, even when the doors are opened, the access to the ECU and related parts is usually limited and thus performing any maintenance/repair tasks can be difficult and/or time consuming. The cramped working environment, as well as the possibility of the moveable (hinged) panels becoming dislodged, means that there is a significant risk of injury to maintenance personnel.
Still further, the hinged panels must be designed to be operable in high winds, including significant wind gusts. This requirement drives significant weight into the structure, which in turn has an impact on overall fuel consumption of an aircraft to which the engine may be attached.